The need for accurate and timely oil well production data is critical. The extremely erosive and harsh environments in which well pumping systems operate create constant deterioration of the equipment, often resulting in rapid failure. To maintain production rates in the face of this situation, well operators invest substantial resources in well maintenance. For wells using steam drives and waterfloods well servicing is frequently the highest non-energy cost.
Knowledge of the production performance of an individual well on a current basis is the most important tool for maximizing production from the well and optimizing reservoir management. Because of the well-known advantages of prompt, accurate and low-cost performance data, numerous testing systems have been devised. Despite extensive previous efforts, there still remain many unsolved disadvantages, resulting in uncertainly of accuracy of the data, and long testing periods because the sampling procedures were very slow themselves.
Early pioneers in production of oil from wells as early as about 1900 began to measure the performance of their individual wells. The early efforts were little more than collecting well production for a day or so, and measuring the gross output and the relative amounts of water and oil with a dip stick or tape measure. That method is still widely used, but is not truly sufficient when optimum and most economical production is the objective.
Open tank systems can indeed accurately measure the output of low production rate wells, but they take a very long time to collect the sample. Worse, production conditions can vary widely during that long period. A true production sample representative of a short preselected period of time can not be obtained with this practice.
Beginning in the 1960's this procedure was improved by providing tall, vertical, closed separators and using various mechanical devices to measure the levels and read them out. These largely succeeded because of the advent of pollution control rules, which adversely affected the earlier open tank samplers rather than because of any inherent sampling superiority. The closed samplers simply produced less pollution.
Beginning in the 1980's improved sensing devices became available, and their use improved the accuracy of the procedures but still their collection times were slow, and they did not provide for suitable purging between tests, leading to contaminated samples. Also the potential for measurement errors in low flow rate wells was and is much higher than it should be. Additional problems reside in the complexity and inaccuracies of the more modern sensors and measuring devices, especially at slow flow rates. Because of their sophistication, the initial costs and the costs of maintenance and operation of these newer systems are much higher than they should be.
Especially in periods of low oil prices at the well, it is essential not only to minimize operation and maintenance costs, but also to maximize production both of the well and of its field. Dollars are very scarce in times of low oil prices, and any reduction of costs is not only welcomed but may contribute to the decision to keep a well or field in operation rather than to shut it down.
It is an object of this invention to provide sampling apparatus and method that can obtain a sample which is suitably small to reflect fluid produced in a relatively short time, even from low production rate wells. A single sampler has the capability to service a substantial number of wells, often up to 60 wells, and to provide frequent samples from them. Importantly, the lines leading to it are fully purged of fluid remaining from previous tests as is the apparatus itself so that the sample is truly representative of well production at a very specific time.
This apparatus can be automated to perform its method on a programmed basis without supervision, and can also be programmed to alert the owner to any departure of a well's performance from previous samplings, thereby alerting the operator to potential problems in a particular well.